Tx, these are cute polls and I like the concept work like for 43. In physics, may favorite prime is indeed 137 which is closest to inverse of alpha the FSC (not exact!) I dig that because as a fundamental dimensionless constant it “ought” to make logical sense directly if the universe is logically oriented in theoretical constructs. So it should be e.g. “one” – but instead it’s that ugly number of no clear conceptual significance, *but* it does have significance as an anthropically beneficial value that makes the universe more hospitable to life. That should still be taken as an interesting feature, whatever your conclusions are if any (see more at the name link.) Of course as well should all know, any particular universe existing and not other possible worlds violates the logical principle of sufficient reason … So either they all exist like modal realism/MUH, or Something or “SomeOne” decides what does and what doesn’t, like it or not IMHO.

But “socially” my favorite prime is the magically mysterious occult number 23 as promoted by Robert Anton Wilson cultists and oc-cultists. Yeah, it’s more cool than “13” IMHO, it’s the classier step up. (OK: 23:13 :: Gaga:Ke$ha!) Whatever you think of that shtick, it’s fun!

I just love 7. It’s the only number I know that can only be divided by itself and 1. Err and uh 7. And 5. And thinking about it 11 as well and er 3. Possibly 2 can as well as 9. Hang on, no, 9 divides by 3. So, other than 2,3,5 and 11, only 7 counts. Err and 13…. What exactly did the Romans do for us?

10288065751. It’s an eleven-digit prime, which is fun in its own right, but more importantly, it’s 123456789012 / 12, and thus one of the largest prime numbers one is likely to discover while bored in class with an HP-32.

63265777. When we were in junior high school, and learning about factoring, a friend cobbled up a 12-digit number (all the calculators could handle) for us to factor. We borrowed a prime number table that went up to 1000 from the teacher, and still nothing. Turned out one factor was the above, and the other was 1613. I typed that number into calculator keyboards often enough that I’ll never forget 102047698301. I can’t learn phone numbers any more, but I do remember that.

3139971973786634711391448651577269485891759419122938744591877656925789747974914319422889611373939731 is a 100-digit prime, and it’s prime whether it’s listed forward or backward. Further, if it’s arranged in a ten by ten matrix, through and through – reversible primes.

… each row, column, and diagonal is itself a reversible prime.

Discovered by Jens Kruse Andersen.

I wish I figured that out by myself, but I must give credit where credit is due. Our fellow American Pat Ballew, who teaches Mathematics to people at a US Defense Department base near Cambridge in the UK, taught me that. You can see the matrix at his blog post: here.

Oops, the number was cut off, much like Physicists do with infinities, unlike we Engineers, who according to you have “9” as a fav prime number. Why so cheeky? Are you afraid of the competition? I’m putting you on notice that I’m reporting you to The Engineering Anti-Defamation League. Expect to be pelted with 45-degree and 30-60 triangles any day now. Maybe a French curve for flavor.

109. My youngest daughter rides horses that jump over fences and gets numbers for various shows. She rolls her eyes when I tell her a number id good because it is a perfect square, or has only single power factors, etc. She thought she could get away with 109, but “it’s Prime!”

1 is my favorite prime number. I’ve been told that it isn’t really prime but I don’t believe it. Seems like it ought to be prime to me so I say it is prime. What other numbers can it be evenly divided by besides 1 & itself? I don’t think there’s an infinite number of prime numbers, either. How could Euclid be so sure there is? Did he count them? Did he make an infinitely long list of prime numbers? I don’t think so. Sure, there’s a lot of them but I think they run out somewhere in the kazillions, or tens of kazillions.

Darwinsdog, Euclid was very clever and figured out how to prove there is no highest prime number. He reasoned using a reductio ad absurdum or self-contradiction proving the converse (as for the proof that square root of two is irrational): suppose there was a highest prime number. That means we can make a product of all of them together and then add one, like 3*5*7*11*13*17 …*P_last + 1. Call that number E. Then try to factor E into primes itself, which we should be able to do since it’s bigger than the alleged “biggest prime.” But if you try, dividing E by each available prime used to construct it, you will of course have a quotient made of other primes multiplied plus some fraction like 1/13, etc, for each one you try to use (and using more just makes it worse.) Hence there can be no biggest prime. These ancient greats were very clever thinkers.

That is pretty crazy. I’d have been impressed if the number broken up in just ten bits were all primes. But, backwards and forwards AND vertically backwards and forwards AND diagonally backwards and forwards both ways? What the … ??

Even more impressive is that someone FOUND that!

Extra credit: How many 100-digit primes are there?

My favorite Prime is 3. It appears in physics far out of proportion than it should. Albert Einstein (wave-particle) and Emmy Noether (symmetry-conservation laws) got us started on the concept of duality, but increasingly triality is being investigated by theoretical physicists.

Books

You've read the blog, now try the books:

Eureka: Discovering Your Inner Scientist will be published in December 2014 by Basic Books. "This fun, diverse, and accessible look at how science works will convert even the biggest science phobe." --Publishers Weekly (starred review) "In writing that is welcoming but not overly bouncy, persuasive in a careful way but also enticing, Orzel reveals the “process of looking at the world, figuring out how things work, testing that knowledge, and sharing it with others.”...With an easy hand, Orzel ties together card games with communicating in the laboratory; playing sports and learning how to test and refine; the details of some hard science—Rutherford’s gold foil, Cavendish’s lamps and magnets—and entertaining stories that disclose the process that leads from observation to colorful narrative." --Kirkus ReviewsGoogle+

How to Teach Relativity to Your Dog is published by Basic Books. "“Unlike quantum physics, which remains bizarre even to experts, much of relativity makes sense. Thus, Einstein’s special relativity merely states that the laws of physics and the speed of light are identical for all observers in smooth motion. This sounds trivial but leads to weird if delightfully comprehensible phenomena, provided someone like Orzel delivers a clear explanation of why.” --Kirkus Reviews "Bravo to both man and dog." The New York Times.

How to Teach Physics to Your Dog is published by Scribner. "It's hard to imagine a better way for the mathematically and scientifically challenged, in particular, to grasp basic quantum physics." -- Booklist "Chad Orzel's How to Teach Physics to Your Dog is an absolutely delightful book on many axes: first, its subject matter, quantum physics, is arguably the most mind-bending scientific subject we have; second, the device of the book -- a quantum physicist, Orzel, explains quantum physics to Emmy, his cheeky German shepherd -- is a hoot, and has the singular advantage of making the mind-bending a little less traumatic when the going gets tough (quantum physics has a certain irreducible complexity that precludes an easy understanding of its implications); finally, third, it is extremely well-written, combining a scientist's rigor and accuracy with a natural raconteur's storytelling skill." -- BoingBoing